Enhanced active scanning in wireless local area networks

ABSTRACT

A method for active scanning in a wireless network may include two transmitters. In such a method, the following steps may take place: initiating active scanning on at least one of a plurality of channels; waiting to transmit a first probe request on a first channel of the plurality of channels based on a delay timer; receiving at the first STA, while the delay timer is not expired, a probe request from a second STA; and skipping the first probe request on the first channel of the plurality of channels based on information contained in the received probe request from the second STA.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/354,775 filed Nov. 17, 2016, which is a continuation of U.S. patentapplication Ser. No. 14/718,580 filed May 21, 2015, which issued as U.S.Pat. No. 9,622,153 on Apr. 11, 2017, which is a continuation of U.S.patent application Ser. No. 13/789,316 filed Mar. 7, 2013, which issuedas U.S. Pat. No. 9,042,324 on May 26, 2015, which claims the benefit ofU.S. Provisional Application Ser. No. 61/642,275 filed May 3, 2012, U.S.Provisional Application Ser. No. 61/668,285 filed Jul. 5, 2012, U.S.Provisional Application Ser. No. 61/696,567 filed Sep. 4, 2012, and U.S.Provisional Application Ser. No. 61/749,064 filed Jan. 4, 2013, thecontents of which are hereby incorporated by reference herein.

BACKGROUND

In IEEE 802.11, there are factors that may adversely impact performanceand user experience in several different scenarios. The length of time(for example, up to several seconds) required for IEEE 802.11 toestablish an initial connection for a user's device may adversely affectuser experience. For example, using interactive sessions (for example, aSkype video), a connection may not be able to be maintained whenswitching from another network, for example, third generation (3G) toWLAN. Another example where the link setup process may adversely impactperformance is a requirement for supporting a large number of userssimultaneously entering an extended service set (ESS) and securelyproviding the users' initial authentication.

SUMMARY

A method for active scanning in a wireless network may include twotransmitters. In such a method, the following steps may take place:initiating active scanning on at least one of a plurality of channels;waiting to transmit a first probe request on a first channel of theplurality of channels based on a delay timer; receiving at the firstSTA, while the delay timer is not expired, a probe request from a secondSTA; and skipping the first probe request on the first channel of theplurality of channels based on information contained in the receivedprobe request from the second STA.

The above method may further include, on a condition that a proberesponse destined for the second STA, transmitted by the AP in responseto the probe request from the second STA is not detected at the firstSTA prior to an expiration of the delay timer, transmitting the firstprobe request on the first channel of the plurality of channels.

In another embodiment a first station (STA) is provided that isconfigured to perform active scanning for an IEEE 802.11 access point(AP). The first STA may include: a processor configured to initiateactive scanning on at least one of a plurality of channels and to waitto transmit a first probe request on a first channel of the plurality ofchannels based on a delay timer; a receiver configured to receive, whilethe delay timer is not expired, a probe request from a second STA; andthe processor further configured to skip the first probe request on thefirst channel of the plurality of channels based on informationcontained in the received probe request from the second STA.

The above first STA may be further configured to transmit the firstprobe request on the first channel of the plurality of channels on acondition that a probe response, transmitted by the AP, is not detectedat the first STA prior to an expiration of the delay timer.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawings.

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A;

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A;

FIG. 2 shows an example of an IEEE 802.11 link setup procedure;

FIG. 3 shows an example of active scanning;

FIG. 3A shows an initial link setup element;

FIG. 4 shows an example of station and access point ranges;

FIG. 5 shows an example of Probe Response cancellation;

FIG. 6 shows an example of Probe Request cancellation;

FIG. 7 shows another example of Probe Request cancellation;

FIG. 8 shows an example of a FILS EDCA parameter set informationelement;

FIG. 9 shows an Access Option Information Element;

FIG. 10 shows Spec i Fields of an Access Option IE;

FIG. 10A shows an ILS Element design;

FIG. 11 shows a first example of a simplified probe request frame with adifferent description field;

FIG. 12 shows a second example of a simplified probe request frame witha different description field;

FIG. 13 shows an example of a difference field/IE in a simplified proberequest frame;

FIG. 14 shows a difference field/IE in a simplified probe request frame;

FIG. 15 shows an example of a simplified probe response frame with adifference description field;

FIG. 16 shows an example of a simplified probe response frame with adifference description field;

FIG. 17 shows a difference field/IE in simplified probe response frame;and

FIG. 18 shows a difference field/IE in simplified probe response frame.

DETAILED DESCRIPTION Introduction

In wireless communications and particularly in Institute for Electricaland Electronics Engineers (IEEE) 802.11 protocols, which are informallyknown as Wi-Fi, it is often required that network entities, such asaccess points (APs) be able to provide connectivity to a large number ofusers. Users typically scan a communications network when establishingconnectivity. Scanning often results in straining network bandwidth andcausing access collision and delay due to the exchange of probe requestsand responses between users and the network.

In the method and apparatus an MLME-SCAN.request primitive with aScanType indicating an active scan may be received and on a conditionthat a ProbeDelay timer is expired or that a PHYRxStart.indicationprimitive is received, a basic access procedure may be performed. In themethod and apparatus, transmission of a Probe Request may be suspendedor cancelled. The suspension of cancellation may be performed viaprimitives between a station management entity (SME) and a media accesscontrol (MAC) layer management entity (MLME), whereby anMLME-Scan-STOP.request primitive may indicate the suspension of activescanning for a current channel. Further in the method and apparatus, aprobe request frame may be transmitted on the condition that a proberesponse frame is not decoded.

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrierFDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a radioaccess network (RAN) 104, a core network 106, a public switchedtelephone network (PSTN) 108, the Internet 110, and other networks 112,though it will be appreciated that the disclosed embodiments contemplateany number of WTRUs, base stations, networks, and/or network elements.Each of the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d may be configuredto transmit and/or receive wireless signals and may include userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106, the Internet 110,and/or the networks 112. By way of example, the base stations 114 a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B, a HomeNode B, a Home eNode B, a site controller, an access point (AP), awireless router, and the like. While the base stations 114 a, 114 b areeach depicted as a single element, it will be appreciated that the basestations 114 a, 114 b may include any number of interconnected basestations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals within aparticular geographic region, which may be referred to as a cell (notshown). The cell may further be divided into cell sectors. For example,the cell associated with the base station 114 a may be divided intothree sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, infrared (IR), ultraviolet (UV), visible light, etc.). Theair interface 116 may be established using any suitable radio accesstechnology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed DownlinkPacket Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1×, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106.

The RAN 104 may be in communication with the core network 106, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. For example, the core network 106may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it will be appreciatedthat the RAN 104 and/or the core network 106 may be in direct orindirect communication with other RANs that employ the same RAT as theRAN 104 or a different RAT. For example, in addition to being connectedto the RAN 104, which may be utilizing an E-UTRA radio technology, thecore network 106 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106 may also serve as a gateway for the WTRUs 102 a,102 b, 102 c, 102 d to access the PSTN 108, the Internet 110, and/orother networks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) andthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired or wireless communications networks ownedand/or operated by other service providers. For example, the networks112 may include another core network connected to one or more RANs,which may employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 130, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In another embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and receive both RF and light signals. It will be appreciatedthat the transmit/receive element 122 may be configured to transmitand/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 104 and the core network 106according to an embodiment. The RAN 104 may be an access service network(ASN) that employs IEEE 802.16 radio technology to communicate with theWTRUs 102 a, 102 b, 102 c over the air interface 116. As will be furtherdiscussed below, the communication links between the differentfunctional entities of the WTRUs 102 a, 102 b, 102 c, the RAN 104, andthe core network 106 may be defined as reference points.

As shown in FIG. 1C, the RAN 104 may include base stations 140 a, 140 b,140 c, and an ASN gateway 142, though it will be appreciated that theRAN 104 may include any number of base stations and ASN gateways whileremaining consistent with an embodiment. The base stations 140 a, 140 b,140 c may each be associated with a particular cell (not shown) in theRAN 104 and may each include one or more transceivers for communicatingwith the WTRUs 102 a, 102 b, 102 c over the air interface 116. In oneembodiment, the base stations 140 a, 140 b, 140 c may implement MIMOtechnology. Thus, the base station 140 a, for example, may use multipleantennas to transmit wireless signals to, and receive wireless signalsfrom, the WTRU 102 a. The base stations 140 a, 140 b, 140 c may alsoprovide mobility management functions, such as handoff triggering,tunnel establishment, radio resource management, traffic classification,quality of service (QoS) policy enforcement, and the like. The ASNgateway 142 may serve as a traffic aggregation point and may beresponsible for paging, caching of subscriber profiles, routing to thecore network 106, and the like.

The air interface 116 between the WTRUs 102 a, 102 b, 102 c and the RAN104 may be defined as an R1 reference point that implements the IEEE802.16 specification. In addition, each of the WTRUs 102 a, 102 b, 102 cmay establish a logical interface (not shown) with the core network 106.The logical interface between the WTRUs 102 a, 102 b, 102 c and the corenetwork 106 may be defined as an R2 reference point, which may be usedfor authentication, authorization, IP host configuration management,and/or mobility management.

The communication link between each of the base stations 140 a, 140 b,140 c may be defined as an R8 reference point that includes protocolsfor facilitating WTRU handovers and the transfer of data between basestations. The communication link between the base stations 140 a, 140 b,140 c and the ASN gateway 215 may be defined as an R6 reference point.The R6 reference point may include protocols for facilitating mobilitymanagement based on mobility events associated with each of the WTRUs102 a, 102 b, 102 c.

As shown in FIG. 1C, the RAN 104 may be connected to the core network106. The communication link between the RAN 104 and the core network 106may defined as an R3 reference point that includes protocols forfacilitating data transfer and mobility management capabilities, forexample. The core network 106 may include a mobile IP home agent(MIP-HA) 144, an authentication, authorization, accounting (AAA) server146, and a gateway 148. While each of the foregoing elements aredepicted as part of the core network 106, it will be appreciated thatany one of these elements may be owned and/or operated by an entityother than the core network operator.

The MIP-HA may be responsible for IP address management, and may enablethe WTRUs 102 a, 102 b, 102 c to roam between different ASNs and/ordifferent core networks. The MIP-HA 144 may provide the WTRUs 102 a, 102b, 102 c with access to packet-switched networks, such as the Internet110, to facilitate communications between the WTRUs 102 a, 102 b, 102 cand IP-enabled devices. The AAA server 146 may be responsible for userauthentication and for supporting user services. The gateway 148 mayfacilitate interworking with other networks. For example, the gateway148 may provide the WTRUs 102 a, 102 b, 102 c with access tocircuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. In addition, the gateway 148 mayprovide the WTRUs 102 a, 102 b, 102 c with access to the networks 112,which may include other wired or wireless networks that are owned and/oroperated by other service providers.

Although not shown in FIG. 1C, it will be appreciated that the RAN 104may be connected to other ASNs and the core network 106 may be connectedto other core networks. The communication link between the RAN 104 theother ASNs may be defined as an R4 reference point, which may includeprotocols for coordinating the mobility of the WTRUs 102 a, 102 b, 102 cbetween the RAN 104 and the other ASNs. The communication link betweenthe core network 106 and the other core networks may be defined as an R5reference, which may include protocols for facilitating interworkingbetween home core networks and visited core networks.

Other network 112 may further be connected to an IEEE 802.11 basedwireless local area network (WLAN) 160. The WLAN 160 may include anaccess router 165. The access router may contain gateway functionality.The access router 165 may be in communication with a plurality of accesspoints (APs) 170 a, 170 b. The communication between access router 165and APs 170 a, 170 b may be via wired Ethernet (IEEE 802.3 standards),or any type of wireless communication protocol. AP 170 a is in wirelesscommunication over an air interface with WTRU 102 d.

A wireless local area network (WLAN) in an infrastructure basic serviceset (BSS) mode may have an access point (AP) for the BSS and one or morestations (STAs) associated with the AP. The AP may have access or aninterface to a distribution system (DS) or another type of wired orwireless network that carries traffic in and out of the BSS. Traffic toSTAs that originate from outside the BSS arrives through the AP and isdelivered to the STAs. Traffic originating from STAs to destinationsoutside the BSS is sent to the AP to be delivered to its respectivedestinations. Traffic between STAs within the BSS may also be sentthrough the AP where the source STA sends traffic to the AP and the APdelivers the traffic to the destination STA. The traffic between STAswithin a BSS is peer-to-peer traffic. The peer-to-peer traffic may alsobe sent directly between the source and destination STAs with directlink setup (DLS) using an Institute for Electrical and ElectronicsEngineers (IEEE) 802.11e DLS or an IEEE 802.11z tunneled DLS (TDLS). AWLAN in Independent BSS mode has no AP, and STAs communicate directlywith each other.

DESCRIPTION

An initial link setup process as well as Fast Initial Link Setup (FILS)will be described.

An initial link setup time of less than 100 millisecond (ms) whilemaintaining a Robust Security Network Association (RSNA) security levelis one benchmark desired in IEEE 802.11 communications. The initial linksetup time may be defined as the amount of time required to gain anability to send Internet Protocol (IP) traffic with a valid IP addressthrough an AP. Further, a minimum user load support of at least 100non-AP STAs entering an ESS within 1 second, and successfully conductinga link set-up is one benchmark. In addition, a robustness in thepresence of high background load to provide a link set-up for medialoads of at least 50% is another benchmark.

A FILS process may comprise five phases: AP discovery, networkdiscovery, additional timing synchronization function (TSF),authentication and association, and higher layer IP setup.

FIG. 2 shows an example of an IEEE 802.11 link setup. In FIG. 2,Extensible Authentication Protocol (EAP) is used. Shown in FIG. 2 arethe five phases: AP discovery 202 which may be achieved using eitheractive scanning or passive scanning by the STAs, network discovery 204,additional TSF 206, authentication 208 and associations 210, and higherlayer IP setup 212.

The description will now describe active scanning and FILS in moredetail.

There may be two types of scanning: active scanning and passivescanning. Active scanning and FILS are described herein. Passivescanning may be characterized as follows:

(1) A STA may not transmit any signal to an AP,

(2) A STA tunes to each channel, for example, each channel on thecandidate channel list and waits for the Beacon frames, and

(3) All beacons received may be buffered to extract information aboutthe BSS that sent the beacons.

In passive scanning there is a low overhead and the absence of frameexchanges. Additionally, there is potential slowness and scanningdepends on the beacon interval.

Active scanning is characterized as follows:

(1) On each channel, a STA may send a Probe Request after gainingaccess,

(2) The STA may wait for a Probe Response, and

(3) A Probe Response may be a unicast management frame that needs to beacknowledged (ACKed).

In active scanning, there may be increased speed compared to a beacon asit is designed as one-on-one, and there is also high overhead and activescanning may not be designed for congested scenarios.

At the end of a scanning process, a scan report may be generated, whichlists all discovered BSSs and their parameters. These parameters may be:

BSS identification (BSSID), Service Set ID (SSID), BSS type, beaconinterval, timing parameters, physical layer (PHY) parameters, and thelike. The STA may choose a BSS or AP to join according to a criterion.

The description will now describe enhanced active scanning.

FIG. 3 shows an example of active scanning. A filter list may be addedto Probe Request frames 304 to enable a requesting STA to define the APsthat may respond more precisely. A transmitter 302 of the Probe Requestframe 304 may indicate a Max Channel Time for which it may be availableto receive Probe Response frames 306. The transmitter 302 of the ProbeRequest frame 304 may cancel the transmission of a pending ProbeResponse frames 306 by sending a Probe End frame to the AP(s), thusavoiding unnecessary retransmissions of probe responses if thetransmitter of the Probe Request frame switches to scan another channel.

A Probe Response 306 may be transmitted to a broadcast address and aProbe Response frame may contain information from other BSSs. If an AP308 overhears a Probe Response 306 including information from its BSS,the AP may cancel the transmission of its Probe Response frame. If an AP308 receives multiple Probe Request frames 304, the AP 308 may transmitone Probe Response frame 306 as a response to the multiple requests.Similarly a beacon may be used as a probe response, thus eliminatingduplicate transmission of the same information. Additionally, ProbeResponse frames may include information regarding BSSs whose primarychannel is other than the scanned channel so that the number of channelsto be scanned may be reduced.

The description will now describe active scanning parameters.

Active scanning will now be described. A primitive, referred to hereinas an MLME-SCAN-STOP.request, will also be described herein. TheMLME-SCAN-STOP.request primitive parameters are as follows:MLME-SCAN-STOP.request (ScanStopType, BSSID, SSID, SSIDList, HESSID,Mesh ID, Filter List, VendorSpecificlnfo). Table 1 shows the type, validrange, and description of the parameters of the MLME-SCAN-STOP.requestprimitive.

TABLE 1 Type, valid range, and description of the parameters of theMLME-SCAN-STOP.request primitive. Name Type Valid range DescriptionScanStopType Enumeration STOP_ALL, Determines whether the SET_CRITERIAreception of all probe responses are cancelled or if new criteria torespond are set. BSSID MACAddress Any valid Identifies a specific orwildcard individual or BSSID. broadcast MAC address SSID Octet string0-32 octets Specifies the desired SSID or the wildcard SSID. SSID List Aset of SSID Previously One or more SSID elements Element defined thatmay be present when dot11MgmtOptionSSIDListActivated is true. HESSID MACAny valid Specifies the desired specific Address individual HESSIDnetwork identifier or MAC address the wildcard network identifier. orthe This field is present when broadcastdot11InterworkingServiceActivated MAC address is true. Mesh ID Octetstring 0-32 octets Only present if BSSType = MESH or BSSType = ANY_BSS.Specifies the desired Mesh ID or wildcard Mesh ID. Filter ListPreviously Previously The list specifies the HESSIDs, defined definedMesh IDs, SSIDs and BSSIDs that are not allowed to respond to therequest. VendorSpecific A set of Previously Zero or more elements. Infoelements defined

The MLME-SCAN-STOP.request primitive may be generated by an SME for aSTA to stop any ongoing scan process or to set new criteria for anongoing scan process.

The effect of receipt of the MLME-SCAN-STOP.request primitive may be toterminate any ongoing scan procedures and transmit a probe end frame.The confirmation of the scan termination may be provided through anMLME-SCAN.confirm primitive.

A field, referred herein as a “Filter List,” may be added in anMLME-Scan.request primitive. The list specifies the HESSIDs, Mesh IDs,SSIDs and BSSIDs that may ignore the request.

Upon receipt of a MLME-SCAN.request primitive with a ScanType indicatingan active scan, a STA may perform the following for each channel to bescanned:

a) Wait until a ProbeDelay time has expired or a PHYRxStart.indicationprimitive has been received.

b) Perform a Basic Access procedure.

c) Send a probe request to the broadcast destination address with theSSID and BSSID from the MLME-SCAN.request primitive. When the SSID Listis present in the MLME-SCAN.request primitive send one or more ProbeRequest frames, each with an SSID indicated in the SSID List and theBSSID from the MLME-SCAN.request primitive.

d) Set a ProbeTimer to 0 and start the ProbeTimer.

e) If PHY-CCA.indication (busy) primitive has not been detected beforethe ProbeTimer reaches a MinChannelTimeset NAV to 0 and scan the nextchannel. Else, the MLME may issue a MLME-SCAN.received primitive withthe BSSDescriptionSet containing information of the AP when ProbeResponse or Beacon frame is received from the AP for the first time.When ProbeTimer reaches MaxChannelTime set NAV to 0 and scan the nextchannel.

When all channels in the ChannelList have been scanned, the MLME mayissue an MLME-SCAN.received primitive with the BSSDescriptionSetcontaining all the information gathered during the scan. If the MLMEreceives an MLME-SCAN-STOP.request primitive, the STA may transmit theProbe End frame with Terminate All Requests field of the FILS RequestParameters set to 1 and stop the ongoing scanning process. The MLME mayissue an MLME-SCAN.confirm primitive with the BSSDescriptionSetcontaining the gathered information and having the ResultCode set toSCAN_ABORTED.

The description will now describe canceling responses to probe requestsand probe end frame.

Cancelling responses to Probe Request with Probe End will now bedescribed herein. A generator of the Probe Request frame may transmit aProbe End frame to a broadcast address or an individual address. If aSTA that has received the Probe End frame has not started transmittingor is transmitting a Probe Response frame to the transmitter of theProbe End frame, a response to Probe Request frame may be transmitted ona condition that the following criteria are met:

a) The Terminate All Requests field of the BSS Type element in theFilter List of the Probe End frame is set to 0.

b) The STA is an AP STA and the Infrastructure field of the BSS Typeelement in the Filter List of the Probe End frame is set to 0 or anSSID, an BSSID, or a homogeneous ESS identifier (HESSID) of the STA isnot included in a Filter List of the Probe End frame; or

1) The BSS of STA is independent BSS (IBSS) and the IBSS field of theBSS Type element in the Filter List of the Probe End frame is set to 0or the SSID or the BSSID of the STA is not included in a Filter List ofthe Probe End frame; or

2) The STA is a mesh STA and the mesh BSS (MBSS) field of the BSS Typeelement in the Filter List of the Probe End frame is set to 0 or theMesh ID or the MAC Address of the mesh STA is not included in a FilterList of the Probe End frame.

If the above criteria are not met, the receiver of Probe End frame maytransmit or retransmit a response to Probe Request frame once, but itmay be a requirement that the response may not be transmitted orretransmitted more than once.

The description will now describe a simplified probe response.

In a simplified probe response, an AP may send a regular Probe Responseframe in response to a Probe Request sent by a STA, (e.g., STA1). Inresponse to a Probe Request (whether the response simplified or not)from another STA (e.g. STA2), the AP may send a simplified ProbeResponse to STA2, by having a reference to the regular Probe Responsesent earlier. This may occur as long as the AP knows that STA2 islistening to the regular Probe Response. For example, the AP may receivethe Probe Request from STA2 immediately before it sends out the regularProbe Response or the second Probe Request is a simplified Probe Requestthat references to the first Probe Request, indicating that STA2 isrequired be awaken and listening to a channel since it receives thefirst Probe Request.

The simplified Probe Response may include a Probe Response ReferenceField or IE that copies the Sequence Control number in the ProbeResponse that is sent earlier as the reference information, for example.The target recipient or recipients of the Simplified Probe Response mayuse the reference information to uniquely identify the referenced ProbeResponse, which was received earlier.

The description will now describe differentiated initial link setup.

In differentiated Initial Link Setup:

-   -   The AP may include an Initial Link Setup (ILS) element as shown        in FIG. 3A in frames such as beacons, FILS Discovery frames, and        Probe Responses, with the following fields in addition to        element ID 352 and Length 354.    -   Initial Link Setup Category (ILSC) Bitmap 356: a bitmap        containing 8 ILSC bits indicating which ILS Category or        Categories of STAs may attempt to associate with the AP in the        following period.    -   ILS Time 358: an indication a period time during which the STAs        for which ILSC bits set to 0 may not be allowed to attempt to        associate with the AP.

The description will now describe several scenarios that might beencountered in use.

In a first scenario, when a large number of STAs that are seekinginitial link setup enter a BSS simultaneously, the STAs conductingactive scanning may send Probe Request frames to the AP. For example,based on real traffic measurements in a Tokyo train station, the numberof Probe Response packets is about four to five times more than thenumber of Probe Request packets, which indicates that each Probe Requestpacket triggers 4 to 5 Probe Response packets on average. This is aresult of using Probe Request frames with Wildcard SSID. Further, airtime occupancy by Probe Request/Response packets takes about 18.32%. Inaddition, the number of Probe Request/Response packets is about 35% ofthe total packets, which increases the probability of channel accesscollision and delay, hence resulting in latency for active scanning ofAP. It is therefore desirable to avoid unnecessary transmissions ofProbe Request frames sent by the STAs seeking initial link setup. Inaddition, minimizing the transmissions of a Probe Request with WildcardSSID is also desired.

In a second scenario, a STA that successfully receives a response to itstransmitted Probe Request frame may send Probe Request End frames to APsto cancel any pending transmission of responses to a Probe Request.However the STA may not have knowledge of whether the scanning of otherSTAs on the channel is successful or not, (i.e, whether a Probe Responseor Beacon is received or not). Examples are available that show that thecancellation of probe response frames may cause problems for other STAsseeking initial link setup.

FIG. 4 shows an example of station and access point ranges. For example,consider a scenario where STA1 402 is able to hear AP1/BSS1 404 andAP2/BSS2 406, but STA2 408 is not able to hear AP1/BSS1 404 but can hearAP2/BSS2 406. Further, STA1 402 sends a Probe Request that is receivedby AP1 404 and AP2 406 and receives a response to the Probe Request fromAP1 404 successfully including information of AP2/BSS2 406. AP2 406overhears the response to probe request with its BSS sent by AP1 404 andmay not transmit a Probe Response frame to respond to Probe Request fromSTA1 402. However, STA2 408 does not receive the response since it isfar away from AP1 404. After that, STA2 408 sends a Probe request to AP2406. Then, both AP1 404 and AP2 406 receive a Probe End frame from STA1402 before AP2 408 starts the transmission of response to the secondProbe Request.

FIG. 5 shows an example of Probe Response cancellation. STA1 502 sends aProbe Request 504 to AP1 500 and successfully receives the response 505to the Probe Request 504 from AP1 500. STA2 506 sends a Probe request508 to AP1 500. AP1 500 receives a Probe End 510 frame from STA1 502,and cancels the response at 512, before it starts the transmission ofresponse to the second Probe Request 508.

Both examples above show that the cancellation of a probe response maycause delay for STA2's scanning of the AP. Therefore, allowingappropriate cancellation of probe response upon receiving Probe Endframe is desirable to ensure proper operation of active scanning.

In a third scenario, robustness in the presence of high background loadmay be desirable in FILS. Further, it may be desirable to demonstrateproviding a link set-up for media loads of at least 50%. However packetsused to facilitate the FILS process may be of type Management.Management frames may be transmitted using the Access Category (AC)AC_VO. In the presence of high background load, management frames usedin FILS may collide and compete for medium access using the samepriority as other (data or management) frames using AC_VO, which maycause a delay in the initial link setup.

In a fourth scenario, an active scanning scheme using simplified ProbeRequest and Response may be desired. The application of Probe Requestand Response may depend on whether two probe requests or two proberesponses have the same value for most of their parameters or whetherthey have different values for some parameters.

Each of the above scenarios will now be discussed in more detail, withan understanding that the discussion for one scenario may be applicableto others. In the first scenario, a STA may be considered to have apending Probe Request to transmit after receipt of a MLME-SCAN.requestprimitive with ScanType indicating an active scan, but before theconditions of an expiry of ProbeDelay time, or a receipt of aPHYRxStart.indication and obtaining channel access.

There may be three kinds of pending Probe Requests: a probe requesttargeted for a specific SSID/STA, a probe request targeted for an SSIDlist, or a probe request targeted for a wildcard SSID.

A pending probe request or an overheard probe request may be regarded tohave the matched scanning target or parameters if certain conditions aremet.

In a first case: if a pending probe request of interest is targeted fora specific SSID or specific medium access control (MAC) address of asecond STA:

a) The Address 1 field in the overheard probe request may be a broadcastaddress or a specific MAC address of the second STA, and either item b)or item c) below are satisfied.

b) The targeted SSID/STA in the pending request may be a mesh ID/STA,and the Filter List in the overheard probe request may not include themesh ID or the specific MAC address of the second STA in the pendingrequest, and the Mesh ID in the overheard probe request is the wildcardMesh ID or the specific Mesh ID of the second STA in the pendingrequest.

c) The targeted SSID/STA in the pending request may not be a meshSSID/STA, and the Filter List in the overheard probe request may notinclude the specific SSID or the specific MAC address of the second STAin the pending request, and the SSID in the overhead probe request maybe a wildcard SSID, or the SSID in the overhead probe request may be thespecific SSID of the second STA in the pending probe request, or thespecific SSID of the pending probe request may be included in the SSIDList element of the overheard probe request, and the Address 3 field inthe overheard probe request may be the wildcard BSSID or the BSSID ofthe second STA in the pending probe request.

In a second case: if the pending probe request of interest is targetedfor the wildcard SSID:

a) The Address 1 field in the overheard probe request may be a broadcastaddress and either item b) or item c) below may be satisfied.

b) The Mesh ID in the overheard probe request may be a wildcard Mesh IDor the specific Mesh ID of the second STA in the pending request.

c) The targeted SSID/STA in the pending request may not be a meshSSID/STA, and the SSID in the overhead probe request is the wildcardSSID, and the Address 3 field in the overheard probe request is thewildcard BSSID.

In a third case: if the pending probe request of interest is targetedfor a specific SSID list:

a) The Address 1 field in the probe request may be a broadcast addressand either item b) or item c) below may be satisfied.

b) The targeted SSID list in the pending request may be a list of meshIDs/STAs, and the Filter List in the overheard probe request may notinclude the targeted SSID list in the pending request, and the Mesh IDin the overheard probe request may be a wildcard Mesh ID.

c) The targeted SSID list in the pending request may not be a list ofmesh SSID/STAs, and the Filter List in the overheard probe request mayinclude the targeted SSID list in the pending request, and the SSID inthe overhead probe request may be a wildcard SSID, or a specific SSIDlist in the pending probe request may be included in the SSID Listelement of the overheard probe request, and the Address 3 field in theoverheard probe request may be a wildcard BSSID.

In a first possible method regarding the first scenario, with referenceto FIG. 6, in order to reduce the number of Probe request frames, a STA2606 seeking initial link setup may cancel transmission of its ProbeRequest 608 if it overhears a Probe Request frame 604 with matchedscanning target or parameters. Further, the corresponding probe response605 may be received by the STA2 606 as well.

An active scanning procedure, upon receipt of an MLME-SCAN.requestprimitive with ScanType indicating an active scan, a STA2 606 mayperform the following:

For each channel to be scanned:

a) Wait until a ProbeDelay time has expired or a PHYRxStart.indicationprimitive has been received. Additionally, the STA2 606 may cancel anattempt of transmitting its Probe Request 608 for a second STA2 beforethe Probe delay timer 610 expires or a PHYRxStart.indication primitivehas been received if the following conditions are met: The STA2 606overhears a Probe Request frame 604 from STA1 602; The RSSI of thereceived Probe Request frame 604 is no less than a pre-definedthreshold; and the overheard Probe request frame 604 has a matchedscanning target or parameter with the pending probe request.

b) Perform a Basic Access procedure. Additionally, the STA2 606 maycancel an attempt of transmitting its Probe Request 608 for a second STAbefore it gains access to the medium only if the following conditionsare met: The STA2 606 overhears a Probe Request frame 604; The RSSI ofthe received Probe Request frame 604 is no less than a pre-definedthreshold; and The overheard Probe Request frame 604 has matched ascanning target with the pending probe request.

In a) and b) above, cancellation of a probe request may be done throughprimitives between the SME and MLME. Upon overhearing the Probe Requestframe that meet the aforementioned conditions, the SME may generate aMLME-Scan-STOP.request 612 primitive for stopping the active scanning ofthe current channel. (This is one of the ways to cancel the proberequest transmission. There are other ways. For example, the MAC layermay not send the probe request and instead wait for a longer time whilewaiting to receive a response.) This may be achieved by one of thefollowing described by way of example.

In a first example, a new value “Stop current channel” may be added tothe field of ScanStopType in the MLME-Scan-STOP.request 612 primitive.The MLME-Scan-STOP.request 612 primitive may be generated with the fieldof ScanStopType being set to “Stop current channel”.

In a second example, a new value “Stop” is added to the field ofScanStopType, and a new field of “ChannelIndex” is added in theMLME-Scan-STOP.request 612 primitive. The MLME-Scan-STOP.request 612primitive may be generated with the field of ScanStopType being set to“Stop”, and the field of “ChannelIndex” being set to the index of thecurrent channel.

In a third example, a new field of “ChannelList” is added in theMLME-Scan-STOP.request 612 primitive. The MLME-Scan-STOP.request 612primitive is generated with the field of ScanStopType being set to“Set_Criteria”, and the field of “ChannelList” being set to theChannelList in the corresponding MLME-Scan.request excluding the indexof the current channel.

If the probe request is cancelled for the current channel during thewaiting time in steps a) or b) due to the receipt of overheard proberequest with matched parameters/target, the STA may set a ProbeTimer to0 and start the ProbeTimer. If PHY-CCA.indication (busy) primitive hasnot been detected before the ProbeTimer reaches MinChannelTime, then NAVmay be set to 0 and the next channel may be scanned. Otherwise, the MLMEmay issue an MLME-SCAN.confirm 614 primitive with the BSSDescriptionSetcontaining information of the AP when Probe Response or Beacon frame isreceived from the AP for the first time. When ProbeTimer reachesMaxChannelTime, NAV may be set to 0 and the next channel may be scanned.

If the STA2 606 does not overhear any probe request with matchedscanning parameters/target during the wait time in a) or b) above, andthe STA2 606 gains access to a medium, the STA2 606 may send one or moreprobe request frames, each with the SSID and BSSID from theMLME-SCAN.request primitive.

In a second possible method regarding the first scenario, another activescanning procedure will now be described. Upon receipt of anMLME-SCAN.request primitive with ScanType indicating an active scan, aSTA may, for each channel to be scanned, wait until a ProbeDelay timehas expired or a PHYRxStart.indication primitive has been received (alsoreferred to herein as action a) and may perform a Basic Access procedure(also referred to herein as action b), for example, per IEEE 802.11 WLANMAC or PHY procedures. During Action a or Action b, the STA may furthersuspend or cancel an attempt of transmitting its Probe Request beforethe Probe delay timer expires or a PHYRxStart.indication primitive hasbeen received if the following conditions are met: the STA overhears aProbe Request frame (also referred to herein as condition 1), the RSSIof a received Probe Request frame is no less than a threshold, forexample, a predefined threshold (also referred to herein as condition2), or an overheard Probe request has a matching scanningparameters/target with a pending probe request at the STA (also referredto herein as condition 3). The threshold may be set to a reasonably highvalue such that the conditional probability that the STA cannot decodethe Probe Response frame responding to the overheard Probe Request,given that the overheard STA may decode such a Probe Response, is nomore than a desired percentage (for example, 1%).

Alternatively, the STA may use pre-acquired knowledge of a location anda time of the day to further decide whether to suspend or cancel anattempt of transmitting its Probe Request when the aforementionedconditions are met. For example, the STA may know that it is in adensely populated location during peak time (such as a busy trainstation at peak commute time) and may decide to use Probe Requestsuspension/omission when overhearing Probe Request frames with matchingscanning parameters/target. On the other hand, if the STA knows it is ina sparsely populated area during off-peak time (for example, in a parkat 6 am), the STA may decide not to use Probe Requestsuspension/omission.

Alternatively, the STA may determine whether the STA is in an area witha dense population of WiFi devices (for example, IEEE 802.11 devices).If during actions a or b, the average received signal/energy level(within the time PHY_CCA.indicate(BUSY)) is no less than a predeterminedthreshold, S1, then the STA may determine that the STA is in an areawith a dense population of WiFi devices and may use Probe Requestsuspension/omission when the conditions 1-3 are met. For example, thethreshold of the received signal level may be set as:transmit power−pathloss(d)−margin

The value of d may equal a small distance such as 5 or 10 meters(depending on a tradeoff to balance the number of probe requests anddelay of active scanning). For a 5 GHz band in IEEE 802.11, the transmitpower may be 23 decibel milliwatt (dBm) and the pathloss without shadowfading at d=5 m may be 56.5 dB. As such, the threshold may be calculatedas −33.5 dBm-margin.

Alternatively the STA may choose a semi-random time period to send aProbe Request in an area with a dense population of WiFi devices. Therandom period may be dependent on the access class of the STA, forexample, a machine-2-machine (M2M) type STA may send Probe Requests morefrequently than other types of STAs.

The cancellation of the probe request may be performed via primitivesbetween the SME and MLME (or using other methods as noted). Uponoverhearing the Probe Request frame that meets the aforementionedconditions, the SME may generate a MLME-Scan-STOP.request primitiveindicating suspending active scanning of the current channel. To achievesuspending active scanning or indicating suspending active scanning, anew value of “Suspend current channel” may be added to the field ofScanStopType in the MLME-Scan-STOP.request primitive. TheMLME-Scan-STOP.request may be generated with the field of ScanStopTypebeing set to “Suspend current channel”.

Further, a new value of “Suspend” may be added to the field ofScanStopType and a new field of “ChannelIndex” may be added in theMLME-Scan-STOP.request primitive. The MLME-Scan-STOP.request may begenerated with the field of ScanStopType being set to “Suspend”, and thefield of “ChannelIndex” being set to the index of the current channel.

A new field of “ChannelList” in the MLME-Scan-STOP.request primitive mayalso be added. The MLME-Scan-STOP.request may be generated with thefield of ScanStopType set to “Set_Criteria” and the field of“ChannelList” set to the ChannelList in the correspondingMLME-Scan.request excluding the index of the current channel.

After receiving a MLME-Scan-STOP.request primitive indicating suspendingthe active scanning of the current channel, the STA may suspendtransmitting a Probe Request frame and set a ProbeTimer to a value ofcurrent time minus the time it overheard the matched Probe Request framethat caused the suspension and start the ProbeTimer. This is equivalentto setting the ProbeTimer to zero when the matched Probe Request framewas overheard. The STA may keep monitoring the channel before theProbeTimer reaches MinChannelTime and if one of the conditions below hasbeen met, the STA may consider that the AP has already transmitted aProbe Response frame in response to the overhead Probe Request. The STAmay further determine that it cannot decode the transmitted ProbeResponse frame in response to the overhead Probe Request and may,therefore, send its own Probe Request Frame.

Condition 1: The STA has detected the channel medium to be busy for acertain time duration at least a SIFS time after it overheard the ProbeRequest but no valid Probe Response, Beacon or FILS Discovery Frames isdecoded. Further, the STA overhears an ACK from a STA that transmittedthe Probe Request a SIFS after the detected busy channel medium time. Anexample value of the detected channel medium busy time preceding theoverheard ACK is close to the transmission time of a Probe Response,Beacon or FILS Discovery Frame.

Condition 2: The STA overhears an ACK from the STA that transmitted theProbe Request at least T1 time after it overheard the Probe Request. Anexample value of T1 may be close to the transmission time of a ProbeResponse, Beacon or FILS Discovery Frame plus two SIFS time durations.

In order to facilitate condition 2, a field in the Broadcast/MulticastProbe Response frame may be used to indicate the STA that requested theProbe Response so that the requesting STA can respond with an ACK to thereceived Probe Response frame. There may be several ways to identify theSTA that requested the Probe Response:

1. Add a new field or Information Element (IE) in the Probe ResponseFrame that signals the AID or Partial AID (PAID) of the STA whose ProbeRequest triggered the Probe Response.

2. Reuse the Duration/ID field in the MAC header of the Probe ResponseFrame to signal the AID or Partial AID (PAID) of the STA whose ProbeRequest triggered the Probe Response.

3. Indicate the Partial AID (PAID) of the STA whose Probe Requesttriggered the Probe Response in the PAID sub-field on the SIG field inthe PLCP header.

Upon receiving a Broadcast/Multicast Probe Response Frame, the scanningSTA that transmitted a Probe Request should check if the AID/PAIDindication in the received Probe Response Frame matches its AID or PAID.If matched, it should respond with an ACK.

If a PHY-CCA.indication (busy) primitive has not been detected beforethe ProbeTimer reaches MinChannelTime, the STA may send its own ProbeRequest Frame if the average received signal/energy level during channelbusy time before an attempt to transmit a Probe Request is suspended orcancelled is no less than a predetermined threshold, S 1. Otherwise, theSTA may set NAV to 0 and scan the next channel.

If the STA receives a valid Probe Response, Beacon or FILS DiscoveryFrame before the ProbeTimer reaches MinChannelTime, the MLME, may issueMLME-SCAN.confirm primitive with a BSSDescriptionSet containinginformation of the AP when Probe Response or Beacon frame is receivedfrom the AP for the first time. When ProbeTimer reaches MaxChannelTime,the NAV may be set to 0 and a next channel may be scanned.

If the STA does not overhear any probe request with matched scanningparameters/target during the wait time in actions a or b, and the STAgains access to a medium, the STA may send a probe request to thebroadcast destination address, with the SSID and BSSID from theMLME-SCAN.request primitive.

In a third method regarding the first scenario, upon receipt of theMLME-SCAN.request primitive with a ScanType indicating an active scan, aSTA may perform active scanning by generating Probe Request frames andsubsequently processing received Probe Response frames.

For each channel to be scanned, there may be a waiting time period fromthe time at which the STA is ready to scan the channel to the time atwhich the corresponding Probe Request frame is transmitted on to awireless medium, as the transmission of the Probe Request frame may needto wait until the ProbeDelay time has expired or a PHYRxStart.indicationprimitive has been received. Further, the STA may perform a Basic Accessprocedure.

Unnecessary transmissions of Probe Request frames may be avoided and anactive scanning procedure may be accelerated as described herein.

Upon receipt of the MLME-SCAN.request primitive with ScanType indicatingan active scan, a STA may perform actions for each channel to bescanned. During the waiting time period for a STA to transmit a ProbeRequest to the channel to be scanned, if the STA has obtained therequired information of the channel to be scanned, the STA may canceltransmission of its pending Probe Request frame and consider acompletion of its scanning of the channel (for example, by generating anMLME-SCAN.confirm primitive with the BSSDescriptionSet containing all ofthe information of the channels received).

This is shown in summary in FIG. 7, which shows STA1, 702, STA2 706, andAP 700. As shown, STA1 702 has transmitted probe request 704 to the AP700 while STA2 706 is waiting to send a probe request. Upon STA2 706'sdetection of a response to STA1 702's probe request 705 for the sametarget, STA2 706 cancels its own probe request 708. Note that STA2 706'strigger event to cancel its probe request 708 need not be limited to theAP's response 705. The STA2 706 may obtain channel information fromother sources, as discussed herein.

The cancellation 708 can be done through primitives between the SME andMLME (or using other methods as noted). Upon receiving the requiredinformation of the channel to be scanned during the waiting time period,the SME may generate a MLME-Scan-STOP.request 712 primitive indicatingstopping the scanning of the current channel. This can be achieved byone of the following described by way of example.

In a first example, a new value “Stop current channel” is added to thefield of ScanStopType in the MLME-Scan-STOP.request 712 primitive. TheMLME-Scan-STOP.request 712 is generated with the field of ScanStopTypebeing set to “Stop current channel”.

In a second example, a new value “Stop” is added to the field ofScanStopType, and a new field of “ChannelIndex” is added in theMLME-Scan-STOP.request 712 primitive. The MLME-Scan-STOP.request 712primitive is generated with the field of ScanStopType set to “Stop”, andthe field of “ChannelIndex” set to the index of the current channel.

In a third example, a new field of “ChannelList” is added in theMLME-Scan-STOP.request 712 primitive. The MLME-Scan-STOP.request 712primitive is generated with the field of ScanStopType being set to“Set_Criteria”, and the field of “ChannelList” being set to theChannelList in the corresponding MLME-Scan.request excluding the indexof the current channel.

Upon receiving the MLME-Scan-STOP.request 712 primitive, the MLME maycancel the transmission of a pending Probe Request frame 708 on thechannel and generate an MLME-SCAN.confirm primitive with theBSSDescriptionSet containing all of the information of the channelsreceived.

If the STA2 706 has obtained required information of several channels tobe scanned during the waiting time period through other sources duringthe waiting time period for a STA2 706 to actually transmit a ProbeRequest to the channel to be scanned, then the STA2 706 may cancel thetransmission of its pending Probe Request frames 708 on channels whoseinformation is received. The cancellation is done through primitivesbetween the SME and MLME. Upon receiving information of several channelsto be scanned during the waiting time period, the SME may generate aMLME-Scan-STOP.request 712 primitive indicating a stop of scanning ofthe channels. This generation of an MLME-Scan-STOP.request 712 primitiveindicating a stop of scanning of the channels may be achieved by any ofthe following. It may be generated by adding a new “Stop” value to thefield of ScanStopType and a new field of “ChannelList” in theMLME-Scan-STOP.request 712 primitive. The MLME-Scan-STOP.request 712 maybe generated with the field of ScanStopType set to “Stop” and the fieldof “ChannelList” set to the indices of the channels whose information isreceived.

Further, a new field of “ChannelList” may be added in theMLME-Scan-STOP.request 714 primitive. The MLME-Scan-STOP.request 712 maybe generated with the field of ScanStopType set to “Set_Criteria” andthe field of “ChannelList” set to the ChannelList in the correspondingMLME-Scan.request excluding the channels whose information is received.

Upon receiving the MLME-Scan-STOP.request 712 primitive, the MLME maycancel the transmission of its pending Probe Request 708 frame accordingto the parameters in the MLME-Scan-STOP.request 712 (for example, thechannels whose information is received) and generate anMLME-SCAN.confirm 714 primitive with the BSSDescriptionSet containingall of the information of the channels received.

If the STA2 706 (or the SME within the STA2 706) decides that it hasfound an AP 700 to which it may associate, then the STA2 706 (or the SMEwithin the STA2 706) may generate a MLME-Scan-STOP.request 712 primitivewith the field of ScanStopType set to “Stop_All” to stop the entireactive scanning process and proceed to the next steps of link setup (forexample, network discovery, authentication, association, and the like).Otherwise, the STA 706 may go to the next channel and perform activescanning.

The STA2 706 may obtain channel information from other sources via thefollowing:

The STA2 706 may monitor the channel and receive frames that areintended for the STA2 706. For example, the STA2 706 may receivebroadcast frames, which provide channel information, such as, a Beaconframe (including short beacon or FILS beacon/FILS Discovery framecontaining a subset of the Beacon information that is required for theSTA to connect to the AP), a measurement pilot frame, a broadcast ProbeResponse frame, and the like.

Alternatively, the STA2 706 may receive channel information throughanother network interface, if multiple network interfaces are supported.In this instance, certain MLME SAP primitives may be defined to providenotifications to the MAC entity that conducts a scanning procedure.

The waiting time between receiving the MLME-SCAN.request 712 primitiveand the transmission of the corresponding Probe Request frame may beadjusted in order to provide a tradeoff between overhead caused by ProbeRequest/Response frame exchanges and the latency in obtaining therequired channel information. This is particularly useful when there isa large number of STAs that are conducting active scanning and the APmay use broadcasted Probe Response frames and/or other broadcastedframes to provide channel information as its response to received ProbeRequest frames.

The adjustment of the waiting time may be performed by settingappropriate values for a ProbeDelay parameter. Alternatively, the STA2706 may dynamically adjust its waiting time or backoff window/procedurein a channel access procedure based on the STA's assessment about thechannel conditions or other considerations.

In a fourth method regarding the first scenario, a STA conductingscanning may be required to scan all the channels in the ChannelListprovided by the MLME-SCAN.request primitive. Further, the STA may issuean MLME-SCAN.confirm primitive with the BSSDescriptionSet containing theinformation of the channels gathered during the scan. The STA may scanone channel at a time, until all channels in the ChannelList have beenscanned.

An AP may obtain certain knowledge about the channels that are otherthan the AP's own operational channel. An AP may provide the knowledgeof other channels to STA in order to accelerate the scanning process fora STA so that the information of the channels in the ChannelList may begathered.

In channel information provisioning frames, a transmitting STA mayinclude channel information of other channels, in addition to its ownoperational channel. Examples of channel information provisioning framesinclude a Beacon frame including a short beacon or a FILSbeacon/Discovery frame containing a subset of the Beacon informationimportant for the STA to connect to the AP, Probe Response frame,measurement pilot frame, and the like. Channel information of otherchannels may be encoded in an Information Element (IE) included in thechannel information provisioning frames. Similarly, this may also beutilized in passive scanning.

During scanning a channel, if a STA receives required information ofother channels, the SME may generate an MLME-Scan-STOP.request with thefield of ScanStopType set to “Set_Criteria” and a new field of“ChannelList” set to the ChannelList in the correspondingMLME-Scan.request excluding the indices of the channels whoseinformation has been received. For example, during scanning of achannel, for example, Ch-A, if a STA obtains all the requiredinformation of another channel, for example, Ch-B, the STA may skip theexplicit scanning procedure for the channel, for example, Ch-B, and usethe Ch-B information (obtained during the scanning of Ch-A) later inlink setup. Similarly, this may also be utilized in passive scanning.

When scanning a channel such as Ch-A, if a STA obtains some informationof Ch-B but not all required information, then the STA may conductscanning on Ch-B by using SSID information obtained during the scanningof Ch-A so that a Probe Request with Wildcard SSID may be avoided.

A STA conducting active scanning may also provide or signal the STA'sChannelList (as specified in the corresponding MLME-Scan.requestprimitive) in its Probe Request frame to serve as an indicator torequest a STA providing Probe Response to also include the informationof other channels in the ChannelList as well as the channel undercurrent scanning procedure. Such ChannelList may be encoded as an IE inthe Probe Request frame.

In a fifth method regarding the first scenario, a large number of STAsmay enter into a space at the same time and all or most may seek toassess services available to them in the new location (for example, whena train is arriving in a station). It may be assumed that all of theSTAs on the train prior to arrival at the station were connected via anAP on the train and that the AP on the train is aware of its locationand that it has arrived at a station. Hence, the AP on the train may beaware that many STAs on the train may be transferring from the train'sAP to the APs in the station and that many STAs in the station may betransferring from the APs in the station to the train's AP.

In one approach, a STA or multiple STAs may be associated with an APthat is mobile and aware of its location. When the AP approaches alocation where some or all of its STAs may be transferring to a new APor looking for additional services, the AP may anticipate this need andprovide the following services for its associated STA(s) and STA(s) thatmay seek to associate with it.

The AP may send a broadcast message to its associated STA(s) that theyare reaching an area in which additional APs and services may beavailable (i.e. the train is entering the station). This message mayalso inform the STA(s) that the AP may be sending a Probe Request atsome defined time in the future or has sent it in the past. It may alsoindicate that an additional Probe Request may be sent on channels otherthan the channel that the AP and the STA(s) are currently using.

The message may also include information that the AP has about servicesavailable in the area entered. Additionally, the notice that the AP maysend the Probe Request may be used by associated STA(s) to suppresstheir own Probe Request, and may rely on the AP's proxy Probe Request toassess the new environment.

At an appropriate time (for example, the time indicated in the broadcastmessage), the AP may send a proxy Probe Request for all of its STA(s).

The STA(s) may then receive the AP proxy Probe Request, and wait for theProbe Responses from the available AP(s) and services in the area andalso proceed as if the AP proxy Probe Request had been sent by theSTA(s).

The AP may also communicate with the AP(s) or perform a network servicesquery in the new area, either over the air or via a DS. The AP mayindicate that it is arriving in their area (for example, the trainentering their station). Upon receiving this information the AP(s) maynotify their STA(s) that an arriving AP is now present in their area.The APs may then choose to also issue a broadcast message to theirassociated STA(s) as described above, which may be followed by the APsending a probe request as described above.

In another approach, a STA or multiple STAs associated with an AP mayrequest that the AP send a proxy Probe Request for the STA(s). Therequest may be initiated by a Management Frame or it may be piggybackedon to a data, management, or ACK frame from the STA. The STA may alsoindicate any channels and a time that the STA desires the proxy ProbeRequest to be made. When a STA makes the request, the AP may follow asimilar procedure as described herein.

The AP may send a broadcast message to its associated STA(s) that itintends to send out a Probe Request and may indicate when it seeks tosend the Probe Request and which channels it may use to send therequest. Associated STA(s) may suppress their own Probe Requests and mayrely on the AP's proxy Probe Request.

When the AP sends the proxy Probe Request, the STA(s) may then hear theAP proxy Probe Request, and wait for the Probe Responses, then proceedas if they had sent a Probe Request themselves.

In another approach, an AP may receive a message either via the DS orover the air from another AP indicating that the AP is entering its areaor has STA(s) which are looking for services. The AP that sent themessage may also indicate that it has new services to offer the STA(s)associated with the AP receiving the message. Upon receiving thismessage the receiving STA may notify its STA(s) of the information, ormay notify its STA(s) that it will be sending a proxy Probe Request,which may allow its STA(s) to then receive the Probe Response from theAPs and services in the area. It is noted that it may be assumed thatthe AP originating the message may respond to the Probe Request.

In a sixth method regarding the first scenario, when there is no APoperating on the channel to be scanned actively, but the adjacentchannel may cause the scanning STA to scan the channel for theMaxChannelTime, the decision of the scanning STA whether or not tocontinue scanning of the channel beyond the initial scanning time may bebased on whether PHY-RxStart.indication primitive instead ofPHY-CCA.indication (busy) has been received by that time.

Upon receipt of the MLME-SCAN.request primitive with ScanType indicatingan active scan, a STA may use the following procedure:

For each channel to be scanned:

a) Wait until the ProbeDelay time has expired or a PHYRxStart.indicationprimitive has been received.

b) Perform a Basic Access procedure as described herein.

c) Send a probe request to the broadcast destination address, with theSSID and BSSID from the MLME-SCAN.request primitive. When the SSID Listis present in the MLME-SCAN.request primitive, send one or more ProbeRequest frames, each with an SSID indicated in the SSID List and theBSSID from the MLME-SCAN.request primitive.

d) Set a ProbeTimer to 0 and start the ProbeTimer.

e) If PHY-RxStart.indication primitive has not been detected before theProbeTimer reaches MinChannelTime+PHY RX latency, or at least onePHY-RxStart.indication primitive has been detected before the ProbeTimerreaches MinChannelTime+PHY RX latency but all of them are triggered byProbe Request Frames, then set NAV to 0 and scan the next channel, elsethe MLME shall issue MLME-SCAN.confirm primitive with theBSSDescriptionSet containing information of the AP when Probe Responseor Beacon frame is received from the AP for the first time. Note that bythe time ProbeTimer reaches MinChannelTime+PHY RX latency+MAC processinglatency, the scanning STA may determine whether all ofPHY-RxStart.indication primitives detected before the ProbeTimer reachesMinChannelTime+PHY RX latency are triggered by Probe Request Frames. Thevalue of PHY RX latency+MAC processing latency may be smaller than SIFStime, since SIFS time=PHY RX latency+MAC processing latency+PHY TXlatency. When ProbeTimer reaches MaxChannelTime set NAV to 0 and scanthe next channel.

With respect to the second scenario, efficient active scanning will nowbe described. An outstanding Probe Request is a Probe Request that an APreceives from a unique STA that has not been responded to yet, meanwhilethe STA's associated MaxChannelTime for scanning specified in the ProbeRequest has not elapsed yet. In order to reduce premature cancellationof a response to a Probe Request frame, a STA may cancel a response to aProbe Request frame if for each outstanding Probe Request the STAreceives a valid Probe End frame from a corresponding STA that sent theProbe Request.

For example, if a STA receives a Probe End frame and the STA has notstarted transmitting a Probe Response or the STA is currentlytransmitting a Probe Response frame to the transmitter of the Probe Endframe, a response to Probe Request frame may be transmitted if thecriteria below are met:

a) The Terminate All Requests field of the BSS Type element in theFilter List of the Probe End frame is set to 0.

b) The STA is an AP STA and the Infrastructure field of the BSS Typeelement in the Filter List of the Probe End frame is set to 0 or theSSID, the BSSID, or the HESSID of the STA is not included in a FilterList of the Probe End frame; or

(1) The BSS of the STA is an IBSS and the IBSS field of the BSS Typeelement in the Filter List of the Probe End frame is set to 0, or theSSID or the BSSID of the STA is not included in the Filter List of theProbe End frame; or

(2) The STA is a mesh STA and the MBSS field of the BSS Type element inthe Filter List of the Probe End frame is set to 0 or the Mesh ID or theMAC Address of the mesh STA is not included in the Filter List of theProbe End frame.

c) For at least one outstanding Probe Request, either a correspondingProbe End frame has not been received or a corresponding Probe End framehas been received but does not meet conditions a) and b) above.

If the above criteria are not met, the receiver of Probe End frame maytransmit or retransmit a response to Probe Request frame once. However,it may be required that the response may not be transmitted orretransmitted more than once.

With respect to the third scenario, efficient active scanning and a FILSprocess will now be described. Further, Access Category for FILS willnow be described. In order to prioritize the transmission of managementframes used for FILS, an access category called AC_FILS may be used forthe Management frames that are utilized in the FILS process. FILS framesthat may be transmitted using AC_FILS include:

A Probe Request frame or it may be required that the Probe Request framebe only transmitted by a STA that is not yet associated with a BSS.

Probe Response frames.

Authentication frames.

Association Request frames.

Association Response frames.

Action frames for Generic Advertisement Service (GAS) Query/Response orit may be required that Action frames for GAS Query/Response be onlytransmitted by a STA that is not yet associated with a BSS.

Management frames used for Security Setup or it may be required that theManagement frames be only used for Security Setup transmitted by a STAthat is not yet associated with a BSS.

Access Category AC_FILS may be determined by the AP. In order to speedup the FILS process, the AC_FILS may have smaller Arbitration InterFrame Space (AIFS) values, smaller Minimum Contention Windows (CWmin)and

Maximum Contention Windows (CWmax) size compared to Access CategoryVoice (AC_VO). In addition, a transmission opportunity (TXOP) limit,which may be defined for AC_FILS, may be shorter or equal to the TXOPlimit allowed for AC_VO.

Further, because FILS frames are localized to the MAC layer in IEEE802.11 communication, no new AC may need to be assigned. FILS frames maybe transmitted using localized FILS enhanced distributed channel access(EDCA) parameters similar to those described above both internal to theSTA and on a wireless medium external to the STA. It is noted that anAC_FILS access category definition is exemplary herein and may bedefined using different terminology.

The description will now describe an AC_FILS EDCA parameter setinformation element and access option information element. FIG. 8 showsan example of a FILS EDCA parameter set information element. An AC_FILSEDCA parameter set information element and Access Option InformationElement is described herein. An information element to provideinformation on the EDCA parameter sets for AC_FILS, or local FILS EDCAparameters for FILS frames is described herein. The FILS EDCA parameterset information element may contain the following fields:

Element identity (ID) 802. The Element ID serves to identify that thecurrent Element ID is the FILS EDCA parameter set information element.

Length (in bytes of the information ID) 804.

AC Index (ACI) for AC_FILS ACI 806. In order to accommodate availableACs, ACI may be three bits or more to define a new AC. For example, theAC Index for AC_FILS may be 4 bits. It may be required that the ACIfield be optional if only localized FILS EDCA parameters are used forFILS frames.

Arbitration Inter Frame Space (AIFS) Number (AIFSN) 808. For the AIFSNassociated with AC_FILS, the default AC_FILS may be 1.

Exponent CWmin (ECWmin) and exponent CWmax (ECWmax) 810. The ECWmin andECWmax define the CWmin and CWmax, respectively, that STAs desiring FILSwith a current AP should adapt and are defined to be CWmin=2ECWmin−1 andCWmax=2ECWmax−1. CWmin and CWmax may be sufficiently large toaccommodate an expected number of STAs performing FILS operations in acoming period by preventing excessive collisions and retransmissions ofFILS frames since excessive collisions and retransmissions of FILSframes may lead to excessive delays in initial link setup time.

TXOP Limit 812. The TXOP Limit contains the limit of the TXOP associatedwith FILS TXOP.

An AC_FILS or a local FILS EDCA parameter set information element may beincluded in selected beacons, short beacons, FILS Discovery frames,Probe Response frames, or any other type of control or managementframes. A STA may include an AC_FILS or a local FILS EDCA parameter setinformation element in a Probe Request frame, or any other type ofcontrol or management frames. The AIFSN, ECWmin, ECWmax fields may beset to zero in these frames from the STAs to the AP to indicate to theAP that the STAs are capable of expedited FILS.

FIG. 9 shows an Access Option Information Element.

The AP may include other information for UL channel access that may berelated to FILS frames in its beacons, short beacons, probe responseframes or any other type of control or management frames. For example,the AP may indicate one or more beacon intervals or beacon sub-intervalthat may be used for FILS operations only where non-FILS frames may notbe transmitted. In addition, the AP may indicate that a subset of STAsmay conduct FILS operations in one or more beacon intervals or beaconsub-intervals. In another example, the AP may indicate one or morebeacon intervals or beacon sub-intervals that may be used for FILSoperations with higher priority and where non-FILS frames may betransmitted with lower priority than FILS frames. The Access OptionInformation Element may be generalized for all type of STAs and for alltypes for frame transmissions.

The Access Option Information Element may include the following fields:

Element ID 902: ID identifying the IE as an Access Option IE.

Length 904: Length in octets of the remainder of the IE.

Number of Spec Fields 906: the number of Spec Fields contained in theremainder of the IE.

Spec 1-Spec N Field 908: each field contains a set of specifications forSTA access. Each field may include specifications for a set of timeintervals, a set of STAs, a set of traffic, or any combination thereof.

FIG. 10 shows Spec i Fields of an Access Option IE. In FIG. 10, 1≤i≤N.The Spec Field may include the following subfields of schedulinginformation:

Start Beacon Interval 1002: The Start Beacon Interval in which theaccess policy starts. Since a beacon may not always be transmitted atthe TBTT, the Start Beacon Interval may refer to the TBTT of the beaconthat commences the targeted Beacon Interval. Alternatively, thissubfield may include a particular value of the TSF timer.

Offset 1004: The offset of the start of the period in which the accesspolicy starts in microsecond or any other time unit from the beacon, orTBTT or to a reference point of time of the TSF timer.

Duration 1006: Specifies the duration of the period during which theaccess policy is valid.

Repeat Frequency 1008: represents how often the access policy specifiedin the Access Option IE is repeated. The subfield may be defined innumber of beacon intervals or mircoseconds or other time units.

The Schedule Info Subfields may be required, whereas in otherembodiments, the Schedule Info Subfields may not be required. Forexample, when the Access Option IE is contained in a beacon or a shortbeacon or other type of management or control frame to announce that theaccess policies specified are valid for the beacon interval or beaconsub-interval or other durations directly following the transmittedframe.

The Spec Field 1009 may also include:

Allowed STA Types 1010: The types of STAs that are allowed to conductmedium access for the specified interval, priority, traffic, and/or EDCAparameters. Examples of STA types may be FILS STAs, sensor and meterSTAs, cellular offloading STAs, battery-powered STAs, electricalmain-powered STAs, and the like. The Allowed STA Types field may be abit-map indicating the various types of STAs allowed.

IDs 1012: This subfield specifies the ID(s) of a STA or a particulargroup of STAs that are allowed to access the medium for the specifiedinterval, priority, traffic, and/or using the specified EDCA parameters.

Allowed Traffic Types 1014: specifies the traffic types that are allowedaccess medium for the specified interval, STA types, using the specifiedEDCA parameters. For example, some of the allowed traffic types may beFILS frames, AC_VO frames, AC_VI frames, sensor and meter sensor frames,red-alert frames reporting fire or detection of intruders, and the like.The Allowed Traffic Types field may be a bit-map indicating the varioustypes or ACs of traffic allowed.

EDCA Parameters 1016: indicates the different set or sets of EDCAparameters that may be used for the specified interval, STA types,priority, and/or traffic. The EDCA parameter sets may be explicitlyspecified in the Spec i Field. Alternatively, indices of EDCA parametersets specified in FILS EDCA Parameter Set Information Element may beused.

It is noted that the FILS EDCA Parameter Set IE, the Access Option IE orany subset of the fields or subfields thereof may be a subfield orsubsets of subfields of any existing or new IE, or as a part of anycontrol, management frames or MAC/PLCP headers.

The description will now describe STA/AP behavior. An AP that is capableof expedited FILS may determine EDCA parameters such as AIFS, CWmin,CWmax and TXOP Limit for AC_FILS depending on the FILS requirements,current network load, and the like, or an AP may determine the EDCAparameters for FILS frames without requiring that the FILS frames belongto a separate AC. An AP may change the AC_FILS or local FILS EDCAparameters from time to time and may include the AC_FILS or local FILSEDCA Parameter Set and/or Access Option IE in its beacons or shortbeacons or FILS Discovery frames or Probe Responses or other types ofmanagement or control frames.

In addition, before a STA that is capable of expedited FILS, the STAreceives a beacon or other type of management or control frame includingthe AC_FILS or local FILS EDCA parameter set information element and/orAccess Option IE. The STA may send a Probe Request using the defaultEDCA parameters for AC_VO, send a Probe Request using default EDCAparameters specified for AC_FILS or FILS parameters, or set the fieldsof AIFSN, ECWmin, ECWmax in the AC_FILS or local EDCA parameter setinformation element included in the Probe Request to zero.

After a STA that is capable of expedited FILS receives a beacon or ashort beacon or other management, FILS Discovery frame, or controlframes that include the AC_FILS or local FILS EDCA parameter setinformation element and/or the Access Option IE, the STA may obey accesspolicies, such as access intervals, parameters, and the like, set by theAccess Option IE when attempting to conduct any transmissions or mediumaccess. In addition, the STA may send a Probe Request using the EDCAparameters specified for AC_FILS or local FILS frames in the beacon.Further, the STA may set the AC_FILS or local FILS EDCA parameter setinformation element to the values received from an AP to indicate thatit is also capable of expedited FILS.

When the AP capable of expedited FILS receives a Probe Request framefrom a STA including an AC_FILS or local FILS EDCA parameter setinformation element with the AIFSN, ECWmin and ECWmax fields set tozero, the AP may respond with a Probe Response with the AC_FILS or localFILS EDCA parameter set information element including all the AC_FILS orlocal FILS EDCA parameters.

The STAs and the AP may use the AC_FILS or local FILS EDCA parametersand the access policies set by the Access Option IE for the remainder ofthe FILS process. If there are multiple APs in the vicinity, a STA mayadapt the AC_FILS or local FILS EDCA parameters and access policies thatthe STA desires to associate with. The AP may use a different set ofAC_FILS or local FILS EDCA parameters or access policies than advertisedin its beacon for FILS related packet exchanges.

A STA that becomes associated with an AP or has already been associatedwith an AP may obey the most up-to-date access policies set by the mostrecent Access Option IE sent by that AP in all subsequent medium access.

The description will now describe an enhanced ILS element that is analternative to the Access Option Information Element. The ILS Elementdesign discussed above may be further extended and enhanced with aschedule of ILS intervals and the associated parameters. An example ofsuch an enhanced ILS Element is shown in FIG. 10A. The enhanced ILSElement may be included in frames such as Beacon, Short Beacon, ProbeResponse, FILS Discovery frames, or any other type of Control,Management, or other type of frames.

The enhanced ILS element fields may include the following:

Element ID 1050: The Element ID indicating that this is an enhanced ILSelement

Length 1052: The length of the enhanced ILS element

Number of Fields 1054: the number of fields contained in the enhancedILS element

Field 1-Field N 1056: each field may contain specifications for ILS orfor regular traffic for a particular period(s) or beacon subinterval(s)and may have the following subfields:

ILSC Indication 1058: the ILSC Indication subfield may indicate the ISLcategory or categories of the STAs that are allowed to conductassociation with the AP in the period(s) or beacon subinterval(s)indicated in the Schedule subfield. The ILSC Indication 1060 may beimplemented as a bitmap.

AC indication subfield 1060: An AC Indication subfield 1060 may indicatethe access category or categories of traffics that the STAs may transmitin the period(s) or beacon subinterval(s) indicated in the Schedulesubfield. The AC Indication 1060 may be implemented as a bitmap.

Schedule 1062: the Schedule Subfield 1062 may indicate the duration ofthe period(s) or beacon subinterval(s). For example, if duration T1 isspecified in Field 1, duration T2 is specified in Field 2, and assumingthat Period 1 starts at T0 (the starting point T0 may be referenced to atargeted beacon time, or to the end of current packet that contains theenhanced ILS element), then Period 1 may last from T0 to T0+T1 andPeriod 2 may be from T0+T1 to T0+T1+T2. Similarly Period N may be fromT0+ . . . +TN−1 to T0+ . . . +TN−1+TN.

Parameters 1064: the parameters for FILS packets and for non-FILStraffic packets. These parameters may include:

EDCA parameters: EDCA parameters for each of the ILSCs that are allowedin the period(s) and beacon subinterval(s), and for each of ACs that areallowed to be transmitted in the period(s) and beacon subinterval(s);and

AP/BSS: an AP may include the enhanced ILS information for neighboringAPs as a part of neighbor reporting in the enhanced ILS element.

The description will now describe differentiated FILS procedures usingan enhanced ILS element. An AP may include the enhanced ILS element inits beacons, short beacons, FILS Discovery frames, and Probe Responsesto inform all STAs for one or more period(s) and beacon subinterval(s)that:

one or more ILSC(s) of STAs that are allowed to conduct association withthe AP;

and/or the EDCA parameters that the FILS STAs should use for FILSrelated packet exchanges for that period(s) or beacon subinterval(s);

and/or one or more AC(s) that the associated STAs may transmit duringthat period(s) or beacon subinterval(s);

and/or the EDCA parameters that the associated STAs should use for eachof the AC during that period(s) or beacon subinterval(s).

Using the enhanced ILS element, the AP may allocate for differentperiods or beacon subintervals different variation of combinations ofthe various ILSCs of FILS traffic and various ACs of traffics from STAsthat are currently associated. In certain period(s) or beaconsubintervals, the AP may disallow certain ILSC STAs or ACs of traffic,such as AC_BK or AC_BE, to allow faster association process for FILSSTAs or a subset of FILS STAs.

The ILSCs of STAs may be determined by the highest AC of ongoing trafficthat the STA is transmitting/receiving. In another implementation, theILSCs of STAs may be determined by classes of SLAs (Service LevelAgreements) of the STAs, such as premium or regular customers. The ILSCsof STAs may also be determined randomly, or be determined based theirMAC addresses, for example, the 4 LSB or MSB of the STA's MAC address.

The APs in OBSS may coordinate their scheduling of different ILSCs andACs of traffic. An AP may also use enhanced ILS element to indicateneighboring APs' schedules for different ILSCs and ACs of traffic.

A FILS STA that wishes to conduct FILS process, when hearing ProbeResponses, FILS Discovery frames, beacons, short beacons, or other typeframes containing the enhanced ILS element, it may select to associatewith the AP that, among other configurations, has the earliest schedulesfor the ILSC that the FILS STA belongs to. The FILS STA may then adaptthe specified EDCA parameters during the specified period and conductthe FILS process.

The description will now describe autonomous FILS parameter adjustment.A FILS STA may adjust its EDCA parameters autonomously, without a needof receiving any messages or indications. When a STA has lower ILSC,e.g., if it only has non-real time traffic, when it needs to conductFILS process with an AP/BSS that is experiencing a high traffic load,either from associated STAs or from the other STAs conducting initiallink setup, it may autonomously adapt the EDCA parameters of a lowerILSC or a lower AC, in order to assist the reduction of link accesscontention by shaping the bursty link access demands over time.

A FILS STA may invoke the autonomous FILS parameter adjustment based oncertain pre-defined triggers:

Location/time/context based triggers with pre-acquired knowledge, forexample, an FILS STA arrives at a busy train station at a rush hour, ifit has pre-acquired knowledge that the AP/BSS has a high traffic load;and

Monitoring/measurement based triggers, for example, a FILS STA hassensed the wireless medium is highly loaded or highly contentious.

With respect to the fourth scenario, differential probe request frameformats are described as shown in FIGS. 11 and 12. In some instances,some or most of the scanning parameters of a pending probe request of aSTA are the same as those of an earlier received probe request, whereassome parameters are different. In order to allow for more frequentutilization of the simplified Probe Request frames 1110, 1210 (shown inFIGS. 11 and 12) to reduce overhead. A difference description field orIE 1100, 1120 may be used in the simplified Probe Request frame 1100,1200 to indicate the difference between the parameters of the earlieroverheard/received probe request and parameters that the STA seeks tosend in a probe request.

The difference description fields are utilized to indicate thedifference between an earlier overheard/received Probe Request and ProbeRequest to be transmitted in a simplified Probe Request frame. Theframes 1100, 1200 may both contain references to another probe request.In the frame 1100 the reference is in its own field 1112 and in theframe 1200, the reference is in the MAC Header 1214. Note that bothframes 1100 and 1200 contain PL CP headers 1116, 1216 and FCS fields1118, 1218

In a first difference description field for a request approach, thedifference description field in a simplified Probe Request frame 1300,shown in FIG. 13 includes a fixed number of sub-fields 1310, 1320, 1330or IEs each describing the difference of a predefined element in theProbe Request. Each sub-field 1310, 1320, 1330 or IE may not includeElement ID since the sequence and meaning of each field or IE ispre-determined.

STET the difference of each element may be encoded appropriatelyaccording to the nature of the element. For example, the difference inthe parameter of SSID list may be encoded as a one-bit indicator ofplus/minus sign and a subset of SSID list. If the earlier received ProbeRequest frame has the SSID list element={SSID1, SSID2, . . . , SSID10}and the pending Probe Request has the SSID list element={SSID1, SSID2, .. . , SSID8}, then the difference of SSID list parameter may be encodedas one bit indicator as “-” and SSID subset as {SSID9,SSID10}.

In a second difference description field approach for a request, thesimplified Probe Request frame 1400 shown in FIG. 14 includes a variablenumber of sub-fields or IEs each containing an Element ID 1405, 1415,1425 and a description 1410, 1420, 1430 of the difference of thecorresponding element (identified by the Element ID) in the ProbeRequest 1400. The length of the difference description field 1410, 1420,1430 or IE of a particular element is pre-determined (has a one-to-onemapping with the corresponding Element ID).

For each channel to be scanned, there may be a waiting time period fromthe time at which the STA receives a MLME-SCAN.request primitiveindicating an active scan to the time at which the corresponding ProbeRequest frame is transmitted. The transmission of the Probe Requestframe may wait until a ProbeDelay time has expired or aPHYRxStart.indication primitive has been received and the STA mayperform the Basic Access procedure.

Upon receipt of the MLME-SCAN.request primitive with ScanType indicatingan active scan, a STA may use the procedure described herein for eachchannel scanned.

During the waiting time period for a STA to transmit a Probe Request toa channel to be scanned, the STA may check if it has overheard a ProbeRequest sent by another STA. If the STA has not heard a Probe Request,the STA may proceed to transmit a regular Probe Request frame to the AP.The remaining scanning procedure may be the same as that of a regularProbe Request.

If the STA has heard a Probe Request, the STA may compare the parametersin the overheard/received probe request with the parameters the STAwants to transmit in the pending probe request. If the number ofdifferent parameters is greater than K, then the STA may transmit aregular Probe Request frame to the AP. The remaining scanning proceduremay be the same as that of a regular Probe Request.

If the number of different parameters is not greater than K, then theSTA may generate a simplified probe request using the format describedherein with a difference description field.

Upon receiving a simplified Probe Request frame, the AP may use thereference field or IE in the simplified Probe Request frame to retrievethe information of the earlier received reference Probe Request frameand combine that with the difference description field to re-constructthe complete parameters for the simplified Probe Request. The remainingscanning procedure may be the same as that of a regular Probe Request.

Most of a portion of the scanning parameters of a pending probe responsemay be the same as those an earlier received probe response. However,some parameters may be different. In order to allow more frequentutilization of the simplified Probe Response frames 1500, 1600 (shown inFIGS. 15 and 16) to reduce overhead, a difference description field1510, 1610 or IE may be used in the simplified Probe Response frame1500, 1600 to indicate the difference in parameters between the earlierreceived probe response and the simplified probe response.

Two alternatives are described herein to indicate the difference betweenan earlier received Probe Response and a Probe Response to betransmitted in the simplified Probe Request frame. The frames 1500, 1600may both contain references to another probe response. In the frame1500, the reference is in its own field 1512 and in the frame 1600, thereference is in the MAC header 1614. Note that in both frames 1500 and1600 contain PLCP headers 1516, 1616 and FCS fields 1518, 1618.

In a first response approach, shown in FIG. 17, the differencedescription field in the simplified Probe Response frame 1700 includes afixed number of sub-fields 1710, 1720, 1730 or IEs each describing thedifference of a predefined element in the Probe Response 1700. Eachsub-field or IE may not include an Element ID since the sequence andmeaning of each sub-field or IE is pre-determined. One sub-field is theTSF value or timestamp value, which may be the difference or deltabetween the current TSF value and TSF value in an earlier Probe Response(that is, TSFcurrent−TSFearlier) or the current TSF.

If the STA may only keep the earlier received probe response up to amaximum time duration of Tmax microseconds, then the sub-field of deltaTSF value will have the length of └log₂ T_(max)┘ bits or

$\left\lfloor \frac{\log_{2}T_{\max}}{8} \right\rfloor$octets.

In a second response approach, shown in FIG. 18, the differencedescription field in a simplified Probe Response frame 1800 includes asub-field of differential TSF value or timestamp value 1803 followed bya variable number of sub-fields or IEs each containing an Element ID1805, 1825 and description 1810, 1830 of the difference of thecorresponding element (identified by the Element ID) in the ProbeResponse 1800. The length of difference description field 1810, 1830 orIE of a particular element is pre-determined (has a one-to-one mappingwith the corresponding Element ID). The length of the differential TSFvalue sub-field 1803 may be the same as that used in the first approach.

If an AP has transmitted a Probe Response within the last N ms and theAP has a pending probe response to be transmitted to a STA, the AP maycompare the parameters in the earlier transmitted Probe Response withthe parameters it wants to transmit in the pending Probe Response. Thevalue of N is a parameter which may be equal to the time that thescanning STA has been listening to channel. The value of N may berepresented by: ProbeDelay+time elapsed since the Probe Requestcorresponding to the Probe Response of interest was received at the AP+amargin.

If the number of different parameters is greater than K, then the AP maytransmit a regular Probe Response frame to the STA. The remainingscanning procedure may be the same as that of a regular Probe Response.

If the number of different parameters is not greater than K, then the APmay generate a simplified probe response using the format describedherein with a difference description field as described herein.

Upon receiving a simplified Probe Response frame, the STA may use thereference field or IE in the simplified Probe Response frame to retrievethe information of the earlier received reference Probe Response frameand combine it with the difference description field to re-construct thecomplete parameters for the simplified Probe Response. The remainingscanning procedure may be the same as that of a regular Probe Response.

The simplified Probe Response frame may also be used for OBSS. When afirst AP in an OBSS sends a regular Probe Response, a second AP mayoverhear the regular Probe Response sent by the first AP and transmits asimplified Probe Response to another STA or a broadcast address. Thesimplified Probe Response may reference the earlier probe response sentby the first AR The simplified Probe Response may include a ProbeResponse Reference field or IE.

BSSID (or MAC address) of the AP that sent the reference Probe Responseand/or a sequence control number of the reference Probe Response may beused to identify the reference Probe Response:

During the waiting time period for an AP to transmit a Probe Response,the AP may check if it has overheard another Probe Response by anotherAP within the last N ms. N is a parameter which may be equal to the timethat the scanning STA has been listening to channel. The value of N maybe equal to ProbeDelay+time elapsed since the Probe Requestcorresponding to the Probe Response of interest was received at the AP+amargin.

If the AP has not overheard another Probe Response, the AP may proceedto transmit a regular Probe Response frame to the STA. The remainingscanning procedure may be the same as that of a regular Probe Response.If the AP has overheard another Probe Response, the AP may compare theparameters in the earlier overheard Probe Response with the parametersit seeks to transmit in the pending Probe Response. If the number ofdifferent parameters is greater than K, then the AP may proceed totransmit a regular Probe Response frame to the STA. The remainingscanning procedure may be the same as that of a regular Probe Response.

If the number of different parameters is not greater than K, then the APmay generate a simplified probe response using the format describedherein with a difference description field as described herein. Uponreceiving a simplified Probe Response frame, the STA may use thereference field or IE (BSSID/MAC address of the AP that sent thereference Probe Response and/or Sequence control number of the referenceProbe Response) in the simplified Probe Response frame to retrieve theinformation of the earlier received reference Probe Response frame andcombine that with the difference description field to re-construct thecomplete parameters for the simplified Probe Response. The remainingscanning procedure may be the same as that of a regular Probe Response.

In a recovery scheme for a simplified probe response, a STA may notunderstand the simplified probe response it receives from an AP. Uponreceiving a Probe Request from a scanning STA, an AP may send asimplified Probe Response to respond when conditions of using simplifiedProbe Response as described herein are met. After transmission of thesimplified Probe Response, the AP starts a timer, referred to herein asan “ACK timer.” If the AP does not receive an ACK from the scanning STAby the time the ACK timer reaches a predefined value (which may be basedon SIFS or time duration of an ACK or short ACK, for example, SIFSduration+time duration of an ACK or a short ACK), the AP may regard thatthe simplified Probe Response is not understood by the scanning STA, forexample, due to the fact that the reference Probe Response was notreceived by the STA. The AP may then transmit a regular Probe Responseto the scanning STA to recover it from the error case.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

What is claimed is:
 1. A method for use in a first station (STA) for fast initial link setup (FILS), the method comprising: receiving a frame from an access point (AP), the frame comprising an information element, wherein the information element includes access information comprising at least one identifier (ID) corresponding to at least one STA that is allowed to conduct a FILS procedure with the AP and an indication of a specific time interval for conducting the FILS procedure during which the at least one STA is allowed to associate with the AP using one or more FILS frames; and conducting the FILS procedure, including transmitting an association request message to the AP, during the indicated specific time interval; wherein the at least one ID of the at least one STA matches a medium access control (MAC) address of the first STA.
 2. The method of claim 1, wherein the frame is a beacon frame.
 3. The method of claim 1, wherein the frame is a probe response frame.
 4. The method of claim 1, wherein the information element further includes priority information for at least one STA.
 5. The method of claim 1, wherein conducting the FILS procedure comprises transmitting an authentication frame to the AP.
 6. The method of claim 1, wherein conducting the FILS procedure comprises transmitting a probe request frame to the AP.
 7. A first station (STA) configured to perform fast initial link setup (FILS), the first STA comprising: a transmitter; a receiver configured to receive a frame from an access point (AP) comprising an information element, wherein the information element includes access information comprising at least one identifier (ID) corresponding to at least one STA that is allowed to conduct a FILS procedure with the AP and an indication of a specific time interval for conducting the FILS procedure during which the at least one STA is allowed to associate with the AP using one or more FILS frames; and a processor configured to determine if at least one ID of the at least one STA matches a medium access control (MAC) address of the first STA; and the processor further configured to conduct the FILS procedure, including transmitting an association request message to the AP, during the indicated specific time interval on a condition that the at least one ID of the at least one STA matches the medium access control (MAC) address of the first STA.
 8. The first STA of claim 7, wherein the frame is a beacon frame.
 9. The first STA of claim 7, wherein the frame is a probe response frame.
 10. The first STA of claim 7, wherein the information element further includes priority information for at least one STA.
 11. The first STA of claim 7, wherein the transmitter is configured to transmit an authentication frame to the AP, in accordance with the FILS procedure.
 12. The first STA of claim 7, wherein the transmitter is configured to transmit a probe request frame to the AP, in accordance with the FILS procedure.
 13. A method for use in an access point (AP) for fast initial link setup (FILS), the method comprising: transmitting a frame to a first station (STA), the frame comprising an information element, wherein the information element includes access information comprising at least one identifier (ID) corresponding to at least one STA that is allowed to conduct a FILS procedure with the AP and an indication of a specific time interval for conducting the FILS procedure during which the at least one STA is allowed to associate with the AP using one or more FILS frames; and receiving at least one FILS frame, including an association request frame, from the first STA during the indicated specific time interval; wherein the at least one ID of the at least one STA matches a medium access control (MAC) address of the first STA.
 14. The method of claim 13, wherein the frame is a beacon frame.
 15. The method of claim 13, wherein the frame is a probe response frame.
 16. The method of claim 13, wherein the information element further includes priority information for at least one STA.
 17. The method of claim 13, wherein the at least one FILS frame received from the first STA during the indicated specific time interval includes an authentication frame.
 18. The method of claim 13, wherein the at least one FILS frame received from the first STA during the indicated specific time interval includes a probe request frame.
 19. An access point (AP) configured to perform fast initial link setup (FILS), the AP comprising: a transmitter configured to transmit a frame to a first station (STA), the frame comprising an information element, wherein the information element includes access information comprising at least one identifier (ID) corresponding to at least one STA that is allowed to conduct a FILS procedure with the AP and an indication of a specific time interval for conducting the FILS procedure during which the at least one STA is allowed to associate with the AP using one or more FILS frames; and a receiver configured to receive at least one FILS frame, including an association request frame, from the first STA during the indicated specific time interval, on a condition that the at least one ID of the at least one STA matches a medium access control (MAC) address of the first STA.
 20. The AP of claim 19, wherein the frame is a beacon frame.
 21. The AP of claim 19, wherein the frame is a probe response frame.
 22. The AP of claim 19, wherein the information element further includes priority information for at least one STA.
 23. The AP of claim 19, wherein the at least one FILS frame received from the first STA during the indicated specific time interval includes an authentication frame.
 24. The AP of claim 19, wherein the at least one FILS frame received from the first STA during the indicated specific time interval includes a probe request frame. 